Email is dying. Email is not dying. Regardless of where you stand in the ongoing debate, one thing is certain: Unsolicited emails are alive and well. Commonly known as spam emails, junk messages about how to get rich quick, find the perfect partner, etc., continue to invade consumers' inboxes. Approximately 15 percent of the emails that the average person receives are spam emails, according to a recent report by technology research firm The Radicati Group.

To help consumers avoid unwanted messages, email providers have set up spam folders that filter out unsolicited messages. Senders who become labeled as spammers can be blacklisted and blocked from sending more emails. In addition, the federal government passed the CAN-SPAM Act in 2004, requiring consumer emails to contain an unsubscribe option, among other mandates.

As the war between spammers and email recipients rages on, marketers are taking careful steps to make sure their legitimate emails do not get blocked by a spam filter or wind up on a blacklist. Read on to make sure that you are on top of the rules for avoiding the dreaded spam folder.

Compared to newer and flashier channels, such as mobile and social media, email has become the workhorse of marketing tools. Despite the fact that email has appeared to reach a plateau in functionality, the number of people using it is on the rise.

The total number of worldwide email accounts is expected to increase from 3.3 billion in 2012 to more than 4.3 billion by the end of 2016, reports The Radicati Group.

In addition, Forrester Research has predicted investments in email marketing will grow from about $1.7 billion in 2012 to nearly $2.5 billion by 2016. The increased spending is attributed to businesses upgrading their email analytics and launching interactive programs.

Even though more people are expected to open email accounts, when it comes to building subscriber lists, it is common for companies to supplement their lists with addresses purchased from third parties. The reason companies do so is "because emails are cheap and easy to send," explains Chris Selland, senior vice president of corporate development at venture capital and equity firm Hale Global. "Growing a list organically is hard because we all get so much email that people are reluctant to sign up for email lists. Hence the temptation to buy email lists," he notes.

Just because it is easy to purchase email addresses does not mean it is risk-free. "If you're just buying names and blasting emails," Selland adds, "your chances of being blacklisted are very high."

Sender Beware

Domain Name Service Blacklists are lists of Internet Protocol (IP) addresses that alert email servers as to which IP addresses have been linked to spam activities and should be blocked from delivering messages.

An IP address is a unique series of numbers that identifies the server from which emails are sent. Email servers access dozens of blacklists, which use a wide variety of criteria for pulling in IP addresses. The triggers include sending thousands of emails from a brand-new address (spammers are known for moving from one IP address to another), sending numerous emails that remain unopened, or sending emails to an inactive address. Sometimes all it takes is one person tagging an email as spam in order to be blacklisted.

Spam filter rules change frequently, explains Tara Thomas, vice president of marketing at Certain, Inc., a SaaS event management platform provider. Therefore it is "important to keep in mind…which spam filters your audience is most likely using [email providers like Gmail, AOL, and Yahoo! each have their own filter], and to regularly test and monitor your email results in order to pass the most current criteria," she advises.

If your IP address winds up on a blacklist, your emails will bounce back, usually with instructions on how to get further information about the block. You can also check if your IP address has landed on a blacklist. Some of the common blacklist holders are CBL, SpamHaus, SORBS, and SpamCop.

The process for getting removed from a blacklist differs with each list. Sometimes IP addresses are unblocked automatically within a few weeks, or you may need to file an abuse form. You will also need to scour your email logs to find and fix the error (assuming you are not actually spamming email recipients).

Email marketing providers such as Constant Contact, HubSpot, MailChimp, and Silverpop help customers avoid numerous deliverability issues by offering shared IP addresses, monitoring services, and other benefits. However, it is still the marketers' responsibility to keep an eye on the health of their email campaigns.

Warming up Your IP Address

Another way to avoid the spam folder or blacklists is to prepare your IP address's reputation for sending commercial emails. Because spammers are known for blasting emails from one IP address after another to avoid being blocked, most spam filters are now designed to limit or reject emails that are delivered from new IP addresses.

"Using a strong Internet Protocol address or an email service provider [ESP] with a solid IP pool is an important insider tip," maintains Andy Pitre, product evangelist at inbound marketing company HubSpot."A brand-new IP address doesn't have a good enough reputation [sender score] to send commercial email until it's been 'warmed up.&'"

If you are using a new IP address, you should warm up its reputation by first emailing your best recipients, i.e., those recipients who are least likely to mark your email as spam. As your IP address's reputation improves (see "What's My Score?"), gradually increase the number of commercial emails that you are sending to recipients. This process can take several weeks or longer, experts warn.

There are also steps you can take to improve your current sending reputation. When monitoring your subscriber lists, make sure you remove the inactive addresses. Subscribe to your Internet Service Provider's (ISP) feedback loop to receive records of email recipients who have marked your email as spam, and remove them from your list as well.

You should also authenticate your emails to further decrease deliverability issues. Authenticated emails allow ISPs to identify the email sender with a specific domain. Doing so discourages spammers from forging emails with your domain and makes it easier for ISPs to accept your emails.

Authentication protocols vary. Some methods just require a file that can be cross-referenced by a receiver (Sender Policy Framework and Sender ID), while others require codes to be embedded in the email itself (DomainKeys Identified Mail). Email receivers check for different types of authentication, so marketers often employ all of them.

Be Relevant

In addition to getting past built-in spam folders, marketers must contend with consumers themselves. "A marketer's best strategy for avoiding spam filters or bulk folders is to create emails that people want to receive," says Shar VanBoskirk, vice president and principal analyst at Forrester Research. "This means creating messages that meet user needs, not just blasting out messages that promote whatever a marketer has in mind that day."

Charlie Graham, founder and CEO of Shop It To Me, a Web site that alerts subscribers to clothing and accessory sales of their choosing, has staked his business on delivering information that customers want. Based on the understanding that each customer has a different set of preferences, Shop It To Me acts like a personal shopper by sending emails to subscribers about sales items that are tailored to each person's interests.

Graham's strategy is working. Since it was founded in 2004, Shop It To Me has sent approximately 1.5 billion emails to subscribers. It has more than 4 million members and close to 200 retail partners.

Citing competitive reasons, Graham declined to reveal the average click-through rate of his company's consumer emails, but noted that providing customers with relevant information boosts its email open rates and click-to-open lift by 30 percent and 40 percent, respectively.

In addition to relevancy, Graham notes that it is important for sites to make it easy for customers to unsubscribe from email lists. Besides the fact that companies are required by law to allow consumers to opt out from receiving commercial emails, businesses should make it as convenient as possible, he says.

"Don't make it hard for your customers to opt out [or] they'll just hit the spam button," Graham warns. "Even having them type their email address in the opt-out box takes longer than it does to mark an email as spam."

Mind Your Subject Lines

Most marketers are already aware that using words such as free, instant, or babes on a subject line will send their email straight to the spam folder. The new challenge, according to Graham, is avoiding the delete button that smartphone users are prone to use as they quickly scan emails on their mobile devices.

Spam folders operate the same way on smartphones, but it's very easy for people to clean out their inbox while they're standing on line," Graham says. "The screens are also smaller, which means subject lines have to be relevant and shorter—not more than a few words—otherwise your email will probably get deleted." Thomas agrees, noting that the "proliferation of smartphones has elevated email's role in the life of the always-connected consumer."

Nine out of 10 smartphone users check their email and browse the Internet on their phone, according to a June 2012 report by the Pew Internet & American Life Project. And smartphone ownership continues to grow. As of March, 50.4 percent of U.S. mobile subscribers owned a smartphone, up from 47.8 percent last December, Nielsen reports.

Given these statistics, it is crucial that marketers pay attention to the ways their emails appear on mobile devices. In addition to subject lines, the body of an email should be optimized for mobile devices. Keeping in mind that consumers are peering at the email on a small screen, marketers should keep images to a minimum. Embedded links should be well spaced to make it easier for smartphone users to tap on them.

Watch Those Numbers

The Girl Scouts of Southern Nevada provides more than 10,000 girls and volunteers with leadership and team-building activities. Keeping its many members up to date on the latest activities and events according to age group is no easy task. With a distribution list of approximately 15,000 subscribers, email continues to be the most efficient way to keep everyone informed, says Emily Smith, the chapter's chief marketing and development officer.

"We send targeted emails once a week on Wednesday—our prime open time—to each of our age levels, a community email for donors and adult volunteers, and a generic shop email with discounts and specials. In total, that's at least twenty unique emails every month," Smith notes.

Smith and her colleagues use Constant Contact's email marketing platform to manage and deliver the chapter's emails. In addition to running periodic tests and following best practice rules for avoiding the spam folder, keeping a close watch on the email campaigns helps ensure that members continue to find them relevant, Smith maintains.

"We have amazing data because we track everything," she says. "For every [campaign] that goes well, that's great, and for those that don't, you still end up with a wealth of data that you can make improvements with."

The chapter's monitoring process includes tracking the open and click-through rates of its emails weekly. Smith and her colleagues also code each link in the emails so that they can be tracked through Google Analytics to find out which messages are most effective for sales and which age levels are most active (the product team uses this data for designing program products), as well as which items drive the most interest.

As a result of these efforts, email drives more than 20 percent of traffic to the chapter's Web site (making it the second largest driver after search engines) and is responsible for the majority of the online purchases of program and camp sessions, according to Smith.

"I believe email works so well for us because those who sign up for [it] are the ones most interested in our product, and we make sure the information is always relevant," she says. "I don't see that changing any time soon."

What's My Score?

Keeping track of your IP address's reputation is tricky. There are many factors (spam complaints, unsubscribe rates, number of invalid recipients, etc.) that determine whether or not mail servers will accept your email. Luckily, there are a number of online tools that will test your IP address and score its reputation for you. Here are several popular options:

AOL Postmaster AOL provides a Reputation Check Tool that lets you quickly check your current reputation with its mail servers. It also provides troubleshooting tools and information on improving your score. http://postmaster.aol.com/Reputation.php

Barracuda Reputation A sister site of Barracuda Networks, a content security and data storage/protection vendor that counts IBM, Harvard University, and CitiBank among its clients, Barracuda Central lets you look up IP and domain reputations stored on its database. www.barracudacentral.org/lookups

Sender ScoreSender Score is a free service provided by Return Path, a company that specializes in email certification and reputation scoring. Sender Score aggregates data from 60 million mailboxes at a variety of ISPs, as well as spam filtering and security companies. Its algorithm rates the reputation of outgoing mail server IP addresses on a scale of 0 (poorest reputation) to 100. Yahoo!, Hotmail, Cloudmark, Road Runner, Cox, SpamAssassin, and other email networks use Sender Score as part of their filtering decisions. www.senderscore.org